WSP06951

• File Number: 8273.300
• Description: Colorado River Basin Salinity Control - Federal Agencies - USGS
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1985
• Author: USGS
• Title: Ground-Water Contribution to the Salinity of the Upper Colorado River Basin
• Water Supply Pro - Doc Type: Report/Study

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Dissolved-solids concentration=O.7415 :II:
Specific conduclanc9-32.42

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. Value of dissolved-solids concentratfon
and specific: conductance from
chemical analysis

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0.2 0.4 0.6 0.8 1.0
SPECIFIC CONDUCTANCE. IN MICRQMHOS PER CENTIMETER AT 250 CELSIUS

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Figure 4.--Linear regression of specific conductance versus
dissolved-solids concentration: Colorado upper headwaters
subregion.

Flow in the Blue River is ,regulated by Dillon and Green Mountain
Reservoirs. The capacity of Dillon Reservoir is about 254,000 acre-ft, which
is approximately equal to the average annual flow of the Blue River. Dillon
Reservoir stores water for transmountain diversions. Green Mountain Reservoir
is 20 mi downstream from Dillon Reservoir and has a capacity of about 147,000
acre-ft. Green Mountain Reservoir stores replacement water for' the
Colorado-Big Thompson diversion project located near Grand Lake and for
irrigation in the Colorado River basin. The mean annual dissolved-solids
concentration of the Blue River is less than 100 mg(L.

Seven sampling sites were selected in this subbasin (figs. 3 and 5;
table 2). Tne estimated dissolved-solids concentration at the sites upstream
from Dillon Reservoir (sites 1-3) ranged from 42 to 90 mg/L, reflecting the
predominance of igneous rocks in this area. Dissolved-solids concentrations
at the sites downstream from Dillon Reservoir (sites 4-6) were affected by
Dillon and Green Mountain Reservoirs, and estimated values ranged from 68 to
about 120 mg(L. The dissolved-solids concentrations at sites 4 through 6 were
adjusted to avoid the effects of storage in the reservoirs. The adjusted
dissolved-solids concentration ranged from 63 to 65 mg/L. The relatively
small concentrations of dissolved solids at all sites in the Blue River
subbasin are a reflection of the relatively insoluble igneous rocks underlying

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